But ahead of the debate, the latest The Economist/YouGov poll shows the percentage of Republicans who think Bush could win the general election falling.

The poll, released Tuesday, shows only 44 percent of Republicans think Bush could win the general election, regardless of who emerges as the Democratic nominee. That's down from 53 percent from just two weeks ago.

Republicans continue to have confidence in Donald Trump: 74 percent said he could win the general election.

The same is true for Ben Carson, who’s faced a week of critical questions about the veracity of his biography. Three-quarters of Republicans thought Carson had a shot at winning the White House; only 13 percent said he “could never” win.

Florida Sen. Marco Rubio, whose stature in the race received a bump after the Oct. 28 CNBC debate , enjoys reasonable levels of confidence — only 19 percent of Republicans think he could never win the general election.

Slightly more than half of Republicans think Sen. Ted Cruz, who also earned high marks for his last debate performance, could capture the executive office, while 28 percent think he could never make it.

More than half of all respondents felt that former Virginia Gov. Jim Gilmore, South Carolina Sen. Lindsey Graham, former Arkansas Gov. Mike Huckabee, Louisiana Gov. Bobby Jindal, former New York Gov. George Pataki and former Pennsylvania Sen. Rick Santorum could never win.

Asked if any of the candidates should drop out, three-quarters of registered voters who identify as Republicans said yes. Unsurprisingly, the highest percentages of those Republicans felt that the candidates who have consistently qualified for the lower-tier debates, if they’ve qualified for any at all, should drop out.

But among those Republicans who think some candidates should go, there’s even a desire for main-stage debaters to drop out of the primary contest. More than 50 percent thought Kentucky Sen. Rand Paul should exit; a slightly higher percentage thought former Ohio Gov. John Kasich should bow out.

In another bad sign for Bush, nearly half of Republicans who thought some candidates should go thought he should drop out — a higher percentage than for New Jersey Gov. Chris Christie, who’s already dropped off the main stage.

The good news for Rubio and Carson is that the lowest percent of Republicans who thought someone should drop out thought either of them should. YouGov’s online survey reaches respondents who agreed to participate ahead of time, so the sample is not as representative as a randomly conducted telephone survey would be. The sample included registered and unregistered voters of all affiliations. “There could be a significant difference between people who agree to take polls and those who don’t agree,” YouGov’s Joe Williams told CQ Roll Call Tuesday. But as YouGov's Kathy Frankovic writes , "The poll shows a marked decline for the man once thought of as the party’s most likely nominee," with just 3 percent of Republicans picking Bush compared to 8 percent two weeks ago.

The poll surveyed 2,000 respondents online from Nov. 5 through 9 and had a margin of error of plus or minus 3.1 percent.